Angular leaf spot (Phaeoisariopsis griseola)
Symptoms consist of small dark brown spots with angular edges and are often numerous to give the foliage a checker-board appearance. The spots may increase in size, join together, and cause yellowing and necrosis of the affected leaves. This may lead to premature defoliation. When humid, the fungus produces a grey mould on the lower surface of the spots. Infected pods have brown blotches. The disease is favoured by high moisture and moderate temperatures (20-25°C).
The disease is seed-borne.
- Use certified disease-free seed.
- Plough under bean debris after harvest.
- Practise a 2-3 year crop rotation without legumes.
- Do not work in bean fields when the plants are wet.